Pseudoniscus

Pseudoniscus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods.[1][2] Pseudoniscus was regarded as part of the clade Planaterga.[1][3][4][5][2][6] Fossils of the genus have been discovered in deposits of the Silurian period in the United Kingdom, the United States and Estonia. Pseudoniscus is one of the two members of the family Pseudoniscidae, the other being Cyamocephalus.[7][6][1]

Pseudoniscus
Temporal range: Silurian
Restoration of Pseudoniscus roosevelti
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Clade: Prosomapoda
Clade: Planaterga
Family: †Pseudoniscidae
Genus: †Pseudoniscus
Nieszkowski, 1859
Type species
†Pseudoniscus aculeatus
Nieszkowski, 1859
Species
  • †P. aculeatus Nieszkowski, 1859
  • †P. clarkei Ruedemann, 1916
  • †P. falcatus Woodward, 1868
  • †P. roosevelti Clarke, 1902
Synonyms
  • Neolimulus Woodward, 1868

The prosoma of Pseudoniscus covered by a carapace with recurved posterior margin and pointed genal spines. Most of the dorsal feature on the carapce (e.g. ophthalmic ridges, cardiac lobe) are not significantly expressed.[8] At least some species have a median spine in front of the carapace like the close-related Cyamocephalus.[7] Unlike most other synziphosurines with opisthosoma subdivided into a wide preabdomen and narrow postabdomen, the 10-segmented opisthosoma of Pseudoniscus possess undivided, metameric segmentation[8] similar to Pasternakevia.[9] Within Pseudoniscus, P. roosevelti is one of the few synziphosurines that confirmed to have lateral compound eyes,[10] while the remain species lacking unambiguous evidence of it.[8][10]

References
  1. Lamsdell, James C. (2013). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi:10.1111/j.1096-3642.2012.00874.x. ISSN 0024-4082.
  2. Bicknell, Russell D. C.; Pates, Stephen (2020). "Pictorial Atlas of Fossil and Extant Horseshoe Crabs, With Focus on Xiphosurida". Frontiers in Earth Science. 8: 98. Bibcode:2020FrEaS...8...98B. doi:10.3389/feart.2020.00098. ISSN 2296-6463.
  3. Selden, Paul A.; Lamsdell, James C.; Qi, Liu. "An unusual euchelicerate linking horseshoe crabs and eurypterids, from the Lower Devonian (Lochkovian) of Yunnan, China". Zoologica Scripta. 44 (6): n/a. ISSN 0300-3256.
  4. Lamsdell, James C.; Briggs, Derek E. G.; Liu, Huaibao P.; Witzke, Brian J.; McKay, Robert M. (2015). "A new Ordovician arthropod from the Winneshiek Lagerstätte of Iowa (USA) reveals the ground plan of eurypterids and chasmataspidids". The Science of Nature. 102 (9–10): 63. Bibcode:2015SciNa.102...63L. doi:10.1007/s00114-015-1312-5. ISSN 0028-1042. PMID 26391849. S2CID 8153035.
  5. Bicknell, Russell D. C.; Lustri, Lorenzo; Brougham, Tom (2019-12-01). "Revision of "Bellinurus" carteri (Chelicerata: Xiphosura) from the Late Devonian of Pennsylvania, USA". Comptes Rendus Palevol. 18 (8): 967–976. doi:10.1016/j.crpv.2019.08.002. ISSN 1631-0683.
  6. Dunlop, J. A.; Penney, D.; Jekel, D. (2018). "A summary list of fossil spiders and their relatives" (PDF). World Spider Catalog. Natural History Museum Bern. pp. 1–296.
  7. Anderson, Lyall I. (1999-01-01). "A new specimen of the Silurian synziphosurine arthropod Cyamocephalus". Proceedings of the Geologists' Association. 110 (3): 211–216. doi:10.1016/S0016-7878(99)80071-6. ISSN 0016-7878.
  8. Eldredge, Niles; Smith, LeGrande (1974). "Revision of the suborder Synziphosurina (Chelicerata, Merostomata) : with remarks on merostome phylogeny. American Museum novitates ; no. 2543". hdl:2246/2745. Cite journal requires |journal= (help)
  9. "Silurian synziphosurine horseshoe crab Pasternakevia revisited - Acta Palaeontologica Polonica". www.app.pan.pl. Retrieved 2020-10-02.
  10. Bicknell, Russell D. C.; Amati, Lisa; Ortega-Hernández, Javier (2019-11-14). "New insights into the evolution of lateral compound eyes in Palaeozoic horseshoe crabs". Zoological Journal of the Linnean Society. 187 (4): 1061–1077. doi:10.1093/zoolinnean/zlz065. ISSN 0024-4082.


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